It’s ice time on Causeway Street. The Bull Gang can pack away the parquet after the Celtics and Knicks play Game 4 on Sunday. You don’t need Red on Roundball to tell you that this series is not coming back to Boston next week.

Draftmaster/sartorial savant Bill Belichick has a catch-all phrase for those rare occasions when the Patriots submit a terrible performance. The Hoodie will stand at the podium and mumble, “That’s not what we were looking for.’’

This is a polite explanation for what unfolded at the Garden on Friday. Fans came out to see the Celtics shake down the thunder from the banner-festooned rafters. Instead, they got another terrible performance from the Green Team. The Celtics were humbled by the Knicks, 90-76, and now face a potential season-ending Game 4. Two years after thumping their chests and sweeping the Knicks, the broom is on the other size-16 Nike.

“I thought we wanted to play well,’’ said Doc Rivers. “We didn’t. Overall, our effort was there. I thought we did lose our spirit early on. We missed two layups to start the game. I thought we lost our spirit for one stretch in the second quarter. That hurts.’’

“We just have to take it one game at a time,’’ said Jeff Green. “They haven’t won it yet.’’

He did not sound as convincing as Kevin Millar before Game 4 of the ALCS in 2004.

Many times we have talked about the end of this Celtic era and here we are again. Is this the end for Kevin Garnett? Will Danny Ainge be motivated to trade Paul Pierce or Rajon Rondo? Is it time to blow it up? We didn’t think the Celtics were going to win the championship with a Rondo-less team this spring, but we didn’t expect they’d go down like this.

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You have to score points to win basketball games.

The Celtics don’t score points. They had second halves of 25 and 23 points, respectively, in the first two games in New York and last night scored 31 in the first half. Ouch. They are averaging 75 points per game in the series.

It started off as an emotional night. The Celtics hadn’t played at home in 16 days — almost a week before the Marathon bombings. The Green Team canceled its final regular-season home game, which had been scheduled for a day after the explosions.

During Friday night’s national anthem, the Celtics featured a Marathon slide presentation on the big videoboard. After the anthem, several members of the Celtics organization, including Rondo and Ainge, visited with one of the partners in the Celtics ownership group, who had family members injured when the bombs exploded on Boylston Street. It was another demonstration of how small our town became in the midst of this global event. Everyone, it seemed, was touched by the tragedy. More than any other date on the Celtic schedule, this was a night to recognize Heroes Among Us. NBA commissioner David Stern was one of the 18,624 witnesses.

The Celtics did a fine job honoring police, first responders, medical personnel, and all others who’ve helped our city get through its crisis. Unfortunately, the men in basketball uniforms were not up to the task. The Celtics simply don’t have enough good players. Who are we kidding? They have now lost 14 of their last 19 games and have precisely one victory over a team with a winning record in the last seven weeks. The Celtics don’t have a point guard and Avery Bradley is being exposed. The Knicks are better. By a lot.

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The Celts were hoping Garnett would return to the Garden and lead them to victory. In his Celtics career, Garnett is famous for coming back from a road playoff loss with a turnaround game. Going into Friday night, the Celtics were 13-0 when coming home from a playoff loss with Garnett in the lineup. In those 13 games, KG averaged 24 points and 10 rebounds.

Garnett was able to snatch 17 rebounds in 34 minutes.

“I just thought he played so hard,’’ said Rivers.

Still, Garnett made only 5 of 13 shots.

Neither team shot 40 percent in the first quarter which ended with the Knicks leading, 23-18. Carmelo Anthony (he didn’t look overrated in this one) made 2 of 7 shots in the first 12 minutes and had his usual zero assists, but the Celtics made only 14 of their first 40 shots and trailed, 47-31, at halftime. Fans booed them when they came off the floor at intermission.

“We got so frustrated with our offense, we let up defensively,’’ said Rivers.

It only got worse. Anthony (26 points on 12-for-25 shooting, no assists) was Michael Jordan and Larry Bird in the third and fourth quarters as the Knicks shot to a 21-point lead. He was the true Fab Melo. Every time the Knicks needed a basket, Anthony scored.

The Celtics shot 40 percent for the game. They committed 17 turnovers. They are down 3-0.

“We lost our spirit and they made every shot,’’ said Rivers. “I didn’t think we were [mentally tough] tonight. I thought we lost our trust a little bit on both ends.’’